security lighting and zs query

[steveth]

Got to put up some outside security lights at the factory where i do some maintenance. Im fine with circuit design, volt drop, ccc ect, but am just after some advice as to the best fittings to use as ive never put any up before.

the lights will be mounted 20ft up and im after the photocell type, what lights do others use i.e son, halogen, halide? in what circumstances are each best? also im thinking 400 watts are going to light the area up nicelly but how good are the 70's or 150's? what do others use in this factory type setup for outside security lights.

also ive come across a situation what i havent previously, there is a ring circuit available to spur one of the lights from. this would take the form of a fused spur from the socket with a bs1362 fuse protecting the light. the total run to the light would take the zs over the maximum for the 32A bs88 fuse protecting the ring but not (i would imagine) over the max for a 3 amp 1362. but to me the whole ring and spur to light would only seem one circuit, cant make my mind up whether the 1362 allows for the ''high'' zs on the ''one'' circuit.

thanks for any advice.

 

[GaryMo]

Steve, treat the fused connection unit as a distribution point.
The outgoing circuit (outdoor lighting) would then need to disconnect in 5 seconds and have a maximum earth loop value of the rated BS1362 fuse you've chosen to protect it, 3A in this case and 23ohms (18.4ohms 80% ROT).

 

[securespark]

Surely not?

Shouldn't you take the maximum Zs value as the one for the protective device in the DB?

 

[plugwash]

Why? the cable is protected by the 3A fuse so I don't see a problem.

 

[GaryMo]

Surely not?

Shouldn't you take the maximum Zs value as the one for the protective device in the DB?

No, there's a BS1362 supplying the circuit. The fused connection unit is a distribution point, much in the same sense as a distribution board. You wouldn't use the maximum Zs value for device protecting a submain for all final circuits leaving a distribution board would you?

 

[Space cat]

The outgoing circuit (outdoor lighting) would then need to disconnect in 5 seconds and have a maximum earth loop value of the rated BS1362 fuse you've chosen to protect it, 3A in this case and 23ohms (18.4ohms 80% ROT).

Purely from a circuit theory viewpoint, the 3 amp fuse determines the maximum loop resistance but --

All the wiring must be included in the resistance calculation, not just the stuff beyond the fuse - or is that what you meant.

 

[securespark]

That's my point, Astro feline.

The circuit is not just that which is beyond the 1362, but includes that part of the circuit fed by the CU.

Hence you must write the characteristics & values of the CPD supplying that FCU (not the 1362 fuse) on the MWC along with the EFLI reading, checked against the max EFLI value for that CPD.

 

[GaryMo]

Fused connection unit supplied from existing circuit protected by a 32A BS88 fuse. Maximum earth fault loop impedance checked against 32A BS88 with a 0.4s disconnection time. Outgoing circuit from fused connection unit (lighting) fed via 3A BS1362 fuse. Maximum earth fault loop impedance checked against a 3A BS1362 fuse with a 5s disconnection time.

 

[Steve]

Anyway - for the type of light, it depends on the requirements. metal halide gives a crisp white light but are less efficient.

But bear in mind, all discharge lighting is much more efficient than halogen.

Do the lights NEED to be on all night? If not, use a seperate photocell and timer setup. This is what we use at work (70w SOX) - the car park light timer comes on at 5pm, then the photocell turns on the lights at dusk. The timer turns off at 10:20pm. Then the timer comes on at about 6:30am and runs off at 9am - clearly at this time of year the photocell would be off anyway. The photocell also directly controls one SOX light above the cash machine, which stays on all night.

 

[industryspark]

The zs considered for the floodlight part of the circuit should relate to the maximum zs of the BS1362 fuse. To use the zs for the BS88 fuse at the origin of the ring circuit doesnt make sense imo. Just make a note of it on the certificate issued for the work.

 

[Spark123]

Fused connection unit supplied from existing circuit protected by a 32A BS88 fuse. Maximum earth fault loop impedance checked against 32A BS88 with a 0.4s disconnection time. Outgoing circuit from fused connection unit (lighting) fed via 3A BS1362 fuse. Maximum earth fault loop impedance checked against a 3A BS1362 fuse with a 5s disconnection time.

For outside lights wont it will need to be a 0.4s disconnection time?
Something in the back of my mind is saying to me to use the max Zs for a 13A fuse for downstream of the FCU regardless of the fuse size but I'll stand corrected on this!

 

[GaryMo]

For outside lights wont it will need to be a 0.4s disconnection time?
Something in the back of my mind is saying to me to use the max Zs for a 13A fuse for downstream of the FCU regardless of the fuse size.

We're talking floodlighting here so I assume that any exposed-conductive-parts (if applicable) are out of reach by a person standing on the general mass of earth therefore a maximum disconnection time of 5s.

 

[Spark123]

It is a final circuit <32A so 0.4s if it is TN system, 0.2s if it is TT. (As of the 1st of next month )
Under the 16th it will depend on how it is mounted, are they on a tower which can be deemed to be an exposed conductive part?

 

[GaryMo]

But we're still in this month so <5s

 

[Spark123]

OK, I'll give you that one given we don't know how they are mounted.